An LED light-emitting device mainly comprises a combination of a phosphor and an LED chip serving as an excitation light source, and can realize various colors of emission light according to the combination.
Specifically, a white LED light-emitting device, which radiates white emission light, comprises a phosphor in combination with an LED chip that emits light in the blue region. For example, the device comprises a phosphor mixture and an LED chip giving off blue light. In practice, a phosphor emitting yellow light, which is complementary to blue light, is often adopted as the phosphor to produce a pseudo-white LED light-emitting device. Further, a three-wavelength white LED device is also developed which comprises an LED chip emitting blue light, a green- or yellow-light emitting phosphor and a red-light emitting phosphor.
As an example of the red-light emitting phosphor, K2SiF6:Mn phosphor is known. The phosphors used in the white LED light-emitting device are required to sufficiently absorb light radiated from the LED chip serving as an excitation light source and also to emit visible light highly efficiently. In addition, if used for illumination, the white LED device preferably comprises two or more kinds of the phosphors in view of color rendering properties, which determine apparent colors of illuminated objects.